Visualization during an operation such as bone resection is important for ensuring that the required amount of resection occurs in the required locations without excess resection in any location. However, direct optical visualization is generally not possible, and effective real-time computerized visualization via 3D modeling has been difficult to implement due to computational complexity and expense. This latter problem is largely due to the complexity of the geometric modeling used to implement such systems.
Constructive Solid Geometry (CSG) rendering is a term used to describe techniques for displaying complex geometric models by combining other, usually simpler, models via mathematical operations such as the subtraction operation. For example, the result of a bone resection pass with a tool of a certain shape can be modeled as a subtraction of the tool shape from the bone shape. Previous image-space CSG implementations perform the computation for all subtracted models in consecutive steps; however, the performance of this technique degrades as the number of overlapping subtraction models increases. It is possible to improve performance during the subtraction of large number of models by computing a view-dependent subtraction sequence, so that non-overlapping models can be subtracted in the same rendering pass. However, again, the performance of using subtraction sequences depends on the depth complexity of the scene, and the performance improvement becomes negligible when the depth complexity is high.
It will be appreciated that this background description has been created by the inventors to aid the reader, and is not to be taken as a reference to prior art nor as an indication that any of the indicated problems were themselves appreciated in the art.